Physiologic Changes of Pregnancy

Anne McConville M.D.

Question 1

• Which of the following is NOT associated with pregnancy?– A) Systolic ejection murmur– B) Mitral regurgitation– C) Aortic regurgitation– D) Pulmonic Regurgitation – E) Depressed ST segments in the precordial and

limb leads

Answer 1

• C

Cardiac Exam During Pregnancy

• LVH• Accentuated S1, exaggerated S2 splitting• Possible S3 and S4• Leftward displacement of PMI• EKG changes

Question 2

• Which of the following parameters in decreased at term?– A) CVP– B) PCWP– C) SVR– D) LVEDV– E) EF

Answer 2

• C

Hemodynamics During Pregnancy

• SVR decreases• EF increases• PAP/PCWP/CVP no change• LVESV no change• CVP no change• Blood pressure decreases

Question 3

• Cardiac Output is greatest:– A) During the 1st trimester– B) During the 2nd trimester– C) During the 3rd trimester– D) During Labor– E) Immediately after delivery

Answer 3

• E

Hemodynamics During Pregnancy

• C.O. in pregnancy– At end of 1st trimester 35-40% above NP state– At term, 50% above NP state– In labor, 75% above NP state– Immediately after delivery, 150% above NP state– At 24 hours back to pre-labor values– Takes 12-24 weeks to return to NP values

Question 4

• Aortocaval compression starts to become significant at how many weeks EGA?– A) 5 weeks– B) 10 weeks– C) 15 weeks– D) 20 weeks– E) 25 weeks

Answer 4

• D

Aortocaval compression

• Depends on position and weeks gestation– Supine>lateral

• At term, near complete occlusion of IVC• At term, aorta may be compressed as well• LUD important to avoid complications • Supine position associated with 10-20%

decrease in SV and CO• Supine Hypotension Syndrome

Question 5

• Which of the following lung capacities change the least during pregnancy?– A) TV– B) FRC– C) ERV– D) RV– E) VC

Answer 5

• E

Respiratory Changes of Pregnancy

• MV and AV rise during pregnancy • RR unchanged• TV increased • IRV increased• ERV decreased• RV decreased• FRC and TLC decreased• VC unchanged

Question 6

• Plasma volume and red cell volume increase by which of the following percentages during pregnancy?– A) PV,30%; RCV, 30%– B) PV, 30%; RCV, 55%– C) PV, 55%; RCV, 30%– D) PV, 30%; RCV, 15%– E) PV, 55%; RCV, 55%

Answer 6

• C

Hematologic Changes of Pregnancy

• Physiologic anemia of pregnancy• TBV 94ml/kg • Term H/H = 11.6/35.5• Plasma proteins decrease • Compensated DIC• Gestation thrombocytopenia• All clotting factors increased EXCEPT:

– II, V unchanged (thromboplastin antecedent)– XI, XIII decreased (fibrin stabilizing factor)

• PT, PTT shortened, TEG shows hypercoaguable• BT unchanged• FDP increased

Question 7

• Which agent is the most useful for raising the gastric pH just before induction of GA for emergency cesarean section?– A) Cimetidine– B) Metoclopramide– C) Ranitidine– D) Sodium Citrate– E) Magnesium hydroxide and aluminum hydroxide

Answer 7

• D

Gastrointestinal Changes of Pregnancy

• Reduced tone in lower esophageal high-pressure zone (LEHPZ)

• Gastric emptying is not altered at any time during pregnancy. Decreased during labor.

• Esophageal and intestinal peristalsis are slowed• 40% of parturients have constipation• Gastric volume unchanged. Increased in labor.• Gastric pH unchanged. Gastric pH increased in

labor.

Question 8

• Which of the following is no increased during pregnancy?– A) Kidney Size– B) Renal Plasma Flow– C) Creatinine Clearance– D) BUN– E) Glucose excretion

Answer 8

• D

Renal Changes of Pregnancy

• Kidneys enlarge by as much as 30%• GFR and renal plasma flow increase

dramatically• Creatinine clearance increased to 150-

200ml/min over the normal 120 ml/min • BUN and creatinine fall to 8-9 and 0.5-0.6.• Total protein and albumin excretion are higher.• Glucose excretion is increased• Acid-base

Question 9

• Which of the following is true regarding the parturient?– A) MAC for inhaled anesthetics is decreased by 75%– B) Parturients have decreased levels of endorphins,

rendering them more sensitive to pain– C) Less local anesthetics are required to produce

similar results with neuraxial blockade– D) Spinal CSF volume is increased– E) Parturients do not depend on the sympathetic

nervous system for maintenance of hemodynamic

Answer 9

• C

Nervous System Changes of Pregnancy

• MAC decreased 40%• Pain threshold increased• Reduced local anesthetic requirements for

neuraxial blockade• Increased epidural fat, engorgement of

epidural veins, reduced CSF volume• Positive lumbar epidural pressure• CSF pressure unchanged, increased during

labor and pushing• Dependent on SNS

Question 10

• Adverse effects on the mother associated with aortocaval compression by gravid uterus include:– A) N/V– B) Pallor– C) Changes in cerebration– D) Decreased in UBF– E) all of the above

Answer 10

• E

Anesthetic implications: Positioning

• Importance of LUD/RUD• Avoid medications that cause venodilation• Hydration

Question 11

• Failed intubation is how many times greater in the obstetric population than the general population?– A) The same– B) Double– C) Four times– D) Eight times– E) Twenty times

Answer 11

• D

Implications of GA

• More parturients are Mallampati IV• Vascular engorgement of airway– Smaller ETT, avoid nasal intubation

• 8X more likely to have failed intubation• Rapid desaturation on induction• MAC decreased by 40%• Reduced pseudocholinesterse activity• Enhanced sensitivity to aminosteroid muscle

relaxants• Reduced sensitivity to vasopressors

Question 12

• A 24 year old primiparous woman is undergoing elective C/S for breech position. 5 minutes after the spinal is placed the BP is 80/40 and HR is 100. The best treatment is– A) Phenylephrine– B) Ephedrine– C) Epinephrine– D) 1000 mL D5LR– E) 1000 mL hetastarch

Answer 12

• A

Implication of Neuraxial Anesthesia

• Rapid onset and longer duration of spinal• Pregnancy does not cause increase LA toxicity• More intervention required to treat

sympathectomy• Prevention versus treatment of hypotension• Phenylephrine vs. ephedrine• Higher doses of vasopressors required• Impaired coughing mechanism with high

levels